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<ul class="breadcrumb"><li><a href="mdoc.html">Index</a></li><li><a href="VL_PLOTSTYLE.html">Prev</a></li><li><a href="VL_PRINTSIZE.html">Next</a></li></ul><div class="documentation"><p>
[RECALL, PRECISION] = <a href="VL_PR.html">VL_PR</a>(LABELS, SCORES) computes the
precision-recall (PR) curve. LABELS are the ground thruth labels
(+1 or -1) and SCORES are the scores associated to them by a
classifier (lager scores correspond to positive guesses).
</p><p>
RECALL and PRECISION are the recall and the precision for
increasing values of the decision threshold.
</p><p>
Set the zero the lables of data points to ignore in the evaluation.
</p><p>
Set to -INF the score of data points which are never retrieved. In
this case the PR curve will have maximum recall &lt; 1.
</p><p>
<a href="VL_PR.html">VL_PR</a>() accepts the following options:
</p><dl><dt>
InludeInf
<span class="defaults">[false]</span></dt><dd><p>
If set to true, data with -INF score is included in the
evaluation and the maximum recall is 1 even if -INF scores are
present.
</p></dd><dt>
Stable
<span class="defaults">[false]</span></dt><dd><p>
If set to true, RECALL and PRECISION are in the samre order of
LABELS and SCORES rather than being sorted by increasing
RECALL. This option implies INCLUDEINF.
</p></dd><dt>
About the PR curve
</dt><dd><p>
This section uses the same symbols used in the documentation of
the <a href="VL_ROC.html">VL_ROC</a>() function. In addition to those quantities, define:
</p><pre>
  PRECISION(S) = TP(S) / (TP(S) + FP(S))
  RECALL(S) = TP(S) / P = TPR(S)
</pre><p>
The precision is the fraction of positivie predictions which are
correct, and the recall is the fraction of positive labels that
have been correctly classified (recalled). Notice that the
recall is also equal to the true positive rate for the ROC curve
(see <a href="VL_ROC.html">VL_ROC</a>()).
</p></dd><dt>
Remark
</dt><dd><p>
Precision (P) is undefined for those values of the
classifier threshold for which no example is classified as
positive. Conventionally, a precision of P=1 is assigned to such
cases.
</p></dd></dl><p>
See also: <a href="VL_ROC.html">VL_ROC</a>(), <a href="VL_HELP.html">VL_HELP</a>().
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